Conventional hard magnetic materials are generally formed from rare earth materials, which are expensive and their supply can be problematic. Hard magnetic materials are widely used in large variety of electrical systems, machines and devices, such as, for example, electric motors, electrical generators, hard disk drives, electric and hybrid vehicles, etc.
There is therefore a need for a high performance hard magnetic material composition having a low rare earth material content.
One such composition is Nd—Fe—B which is a hard magnetic material already used in many industrial applications. To date, the experimental behaviour of exchange-coupled Nd—Fe—B magnetic materials has not matched the predicted magnetic properties.
For example, the predicted magnetic properties of exchange-coupled Nd—Fe—B magnets are considerably higher than the experimental values obtained so far. The predicted values are based on efficient exchange coupling, which can only be obtained at the nanoscale level through nanostructured materials.
It is known to produce Nd—Fe—B magnetic materials using techniques such as melt spinning, ball milling and HDDR methods. These methods involve a series of processing steps such as, for example, homogenization at high temperature, melting, casting, and milling, followed by annealing to obtain the final product. A known problem with these techniques is that they need an excess amount of Nd in order to compensate for the evaporation loss.